The invention is based on a wiper drive with a reversible geared motor.
Wiper systems of motor vehicles are as a rule fastened with a wiper support, a so-called mounting plate, to the body of a motor vehicle. The mounting plate supports a wiper drive with a wiper motor and a transmission built into it, whose driven shaft, as a rule by means of a driving crank and joint rods, drives cranks which are connected to a drive shaft for each wiper. The joint rods are linked to the driving crank by means of two ball-and-socket joints, wherein the joint axes extend coaxially. A lever mechanism of this kind comprised of the cranks and joint rods takes up a correspondingly large amount of structural space in the vehicle due to its structural height.
EP 0 781 691 A1 has disclosed a wiper drive which is comprised of an electric motor with a worm gear and a lever mechanism. An offset driving crank is supported on the driven shaft. A joint rod, which is connected to the driving crank by means of a ball-and-socket joint, is connected at its free end, likewise by means of a ball-and-socket joint, to a crank embodied as a crank plate, which is connected to a drive shaft of a wiper. By means of another ball-and-socket joint, the crank plate is engaged by a second joint rod, which is connected with its free end to a crank, which is fastened to a drive shaft for a second wiper. The lever mechanism comprised of the cranks and joint rods is very expensive and takes up a relatively large amount of structural space. Furthermore, the joint rod that leads from the driving crank to the crank of the first wiper is subjected to the driving forces of both wipers. The first joint rod and its joints must be designed accordingly.
EP 0 683 739 has disclosed a joint in which three joint parts are provided with concentrically arranged ball-shaped bearing surfaces. Each joint part is connected to a joint rod or to a driving crank. The connections of the driving crank and the joint rods require a large amount of axial space in the direction of the common pivot axis.
According to the invention, the wiper drive is comprised of a reversible geared motor whose driven shaft is connected to a driving crank which is embodied as a crank plate and drives two joint rods by means of two joints that are suitably embodied as ball-and-socket joints. These two joint rods are connected to cranks which are each connected to a drive shaft of the two respective wipers. The cranks and joint rods constitute a lever mechanism. The reversible geared motor, which replaces a conventional rotating motor, pivots the installed crank only in a limited angular range, e.g. up to 180xc2x0 around the axis of the driven shaft. As a result, the joints can, according to the invention, be disposed next to each other in one plane on the crank plate, so that a very flat lever mechanism is produced.
According to one embodiment of the invention, the joints on the driving crank plate are disposed at different distances from the driven shaft. As a result, differences in the lever transmission that result from an asymmetrical position of the driven shaft in relation to the drive shafts of the wipers can be balanced out. Furthermore, different kinematics can be produced for a wiper on the driver""s side and a wiper on the passenger side.
As a rule, the geared motor is screwed to a motor mounting plate by means of a screw, while the driving crank is fastened to the driven shaft with a screw. In order to limit the structural height in the direction of the driven shaft, it is suitable to offset the crank platexe2x80x94in fact in such a way that its free end is a greater distance from the motor mounting plate than the part supported on the drive shaft. As a result, a space is created for the fastening screws of the geared motor, without increasing the structural height in the direction of the drive axis. There is also the possibility of fastening ball journals onto the crank plate, which point toward the motor mounting plate and consequently also do not increase the structural space in the direction of the drive axis. This type of articulation is also advantageous if only one joint rod engages the crank plate.
Since the joint rods are each subjected to only the driving forces for one wiper, they can be embodied as thin-walled and lightweight. One embodiment of the invention suggests incorporating the support socket of the ball-and-socket joint into the crank plate. Since the crank plate must be embodied as correspondingly thick in order, if necessary, to transmit double the driving forces, namely for two wipers, the joint balls and the support sockets can be embodied as sufficiently large without increasing the structural space as a result. In this connection, the joint ball can be provided with a pin on one side or can be provided with two diametrically opposed pins. In the second case, the joint rod has a fork-shaped end which is connected to the two pins, e.g. by rivets. The articulating lever can be embodied as very lightweight by being comprised of two bent sheet metal parts which are connected to each other at a central joint extending parallel to the fork-shaped ends.